Purpose :
We recently reported glial membranes on the vitreoretinal surface of aged human retinas that increased in severity in eyes with neovascular age-related macular degeneration (AMD). These subclinical membranes could be precursors to epiretinal membranes and may complicate treatment of neovascular AMD. Understanding what drives the formation of these membranes could improve treatment of AMD and other conditions with epiretinal membranes such as diabetic retinopathy. This study investigated the Müller cell response to tumor necrosis factor alpha (TNFα), which is increased in AMD vitreous and retina.

Methods :
The MIO-M1 immortalized human Müller cell line was used to investigate the Müller cell response to TNFα. A wound healing assay was used to measure cell migration. MIO-M1 cells were treated with TNFα (10-100ng/mL) at time of injury with and without pretreatment for 24hrs prior to injury. Wound images were collected at 0 and 24hrs. Wound areas were measured using Image J at each time point and the percent wound healing calculated. The effects of TNFα (0.1-100ng/mL) on proliferation were determined by counting cells 48hrs after treatment. Müller cells exposed to TNFα (20ng/mL) for 4 or 24hrs were immunocytochemically stained with antibodies against GFAP, vimentin and glutamine synthetase (GS). Images were collected on a Zeiss 710 confocal microscope. T-tests were used to compare each treatment to controls with p<0.05 considered significant.

Results :
Treatment with 100ng/mL TNFα initially after wound injury significantly increased wound healing after 24hrs (p<0.05). Pre-treatment with TNFα increased wound healing as well in a dose-dependent manner with doses of 25-100ng/ml being significant compared to non-treated cells at 24hrs (p<0.05). TNFα (0.1-100ng/mL) did not significantly increase MIO-M1 cell proliferation. A decrease in GS expression was observed at 4hrs but not 24hrs after TNFα treatment. Cells expressing GFAP increased 4hrs after TNFα treatment but not at 24hrs.

Conclusions :
Since TNFα is one of the factors that regulates Müller cell proliferation and migration, it could also be a factor in stimulating Müller cell epiretinal membrane formation. Thus, Müller cell activation by TNFα may stimulate the expression and release of other cytokines, priming Müller cells and astrocytes for epiretinal membrane formation.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.